Postgrad Med J (1992) 68, 22 - 25
D The Fellowship of Postgraduate Medicine,
1992
Changing patterns of malaria in south-east Scotland: implications for practitioner awareness and prophylactic advice Lorna Willocks, Michael Jones, Ray Brettle, Philip Welsby and James Gray Infectious Diseases Unit, City Hospital, Greenbank Drive, Edinburgh, EHIO 5SB, UK
Summary: The medical records of all 229 patients with malaria admitted to the Edinburgh City Hospital between 1969 and 1988 were studied retrospectively. A total of 137 were from Africa, 44 from the Indian subcontinent, 19 from the Far East, 18 from New Guinea, 5 from the Middle East and 3 from South America. The number of yearly admissions rose markedly after 1983, mainly due to an increase in Plasmodiumfalciparum cases. Ninety-four cases (15 with severe parasitaemia) mainly from Kenya and Nigeria were due to P. fakciparum infection and 99 to P. vivax. There were no deaths. A seasonal distribution of onset of fever in patients with P. vivax infections originating from the Indian subcontinent showed that most patients presented during the summer. Prophylaxis had generally been irregular or non-existent but many compliant patients may have been receiving an inadequate dose of chloroquine on a mg/kg body weight basis. General practitioners are Ukely to see at least one case of malaria every 4 years. They are encouraged to seek advice from a specialist unit whenever necessary whether before or after their patient travels abroad. Travellers, in particular to Kenya and Nigeria, and Asian immigrants to the UK returning on holiday to their country of origin should be strongly advised to take regular prophylaxis including on return to the UK. Introduction
The last 20 years have witnessed a dramatic change in the incidence, species proportions, drug resistance and geographical distribution of malaria worldwide.',2 In 1970 only 49 cases of Plasmodium falciparum infection were notified in the UK rising to 1,028 in 1988 with the percentage of UK cases seen at the Hospital for Tropical Diseases, London (LHTD) falling from 65% in 1970 to 30% in 1988 (Chiodini, personal communication). Therefore while the number of cases at LHTD has risen ten-fold, the number of cases of P. falciparum seen elsewhere in the UK has risen twenty-fold. Over the ten years 1977-86 the annual incidence of malaria in the UK increased by 51% from 1,529 to 2,309 cases and the proportion of cases due to P. falciparum increased from one fifth to one third.3 Chloroquine resistance in P. falciparum malaria has become widespread4'5 and it may be increasing in virulence.6'7 The only previous study of malaria in Edinburgh was confined to children.8 We conducted a retrospective survey of malaria presenting in Edinburgh
City Hospital from 1969 to 1988 to determine the extent to which national trends are being reflected in a Scottish Regional Centre. We also examined the monthly incidence of P. vivax malaria to determine whether a seasonal pattern of P. vivax malaria reported elsewhere in the UK9"0 is observed in Edinburgh and the possibility that breakthrough malaria in some patients may be associated with inadequate doses of chloroquine prophylaxis on a mg/kg body weight basis." Methods
Admissions in Edinburgh with malaria for the years 1969-1988 inclusive were identified from Scottish hospital inpatient statistics and City Hospital case notes. The City Hospital Tropical Medicine Unit (1961-1972) and Infectious Diseases Unit (1972 onwards) was the site of referral for patients with malaria from south-east Scotland throughout the period under study. Results
Correspondence: L. Willocks, M.R.C.P. Accepted: 2 September 1991
Of 229 admissions the male to female ratio of 164:65 (i.e. 3: 1) remained constant throughout.
CHANGING PATTERNS OF MALARIA
23
The mean age was 29 years (range 2-80). The Four countries (Nigeria, Kenya, Ghana and number of cases per year rose over the period Tanzania) accounted for 65% of cases. One third studied from a mean of 10.6 patients per year in the (6/15) ofall cases presenting to our Unit with severe first 5 years (53 admissions) to 15.2 patients per parasitaemia or complicated malaria originated year in the last 5 years (76 admissions). The most from Kenya and Nigeria. Most complications marked increase has been since 1983 and was related to thrombocytopenia with subsequent bleeding. Two patients (one of whom required largely due to P. falciparum malaria. exchange transfusion for 30% parasitaemia) from Nigeria had cerebral malaria and renal failure Species requiring dialysis and I from Kenya was dialysed There were 99 cases due to Plasmodium vivax, 94 to for blackwater fever. P. falciparum, 6 to P. ovale, 5 to P. malariae and 3 to mixed infections. Parasite speciation was not Patients returningfrom the Indian subcontinent performed in 22 patients. From 1985 onwards parasites were identified in all cases and comprised Forty-four patients presented from the Indian subcontinent, the annual incidence increasing only falciparum or vivax species. markedly over the first 15 years and falling over the last 5. Most (31) patients were settled immigrants Prophylaxis returning from holidays in their country of origin. Most prophylaxis was inadequate, the most com- Twenty-two had taken no prophylaxis and 8 were mon failure being irregular prophylaxis after return poor compliers. Nine were visitors from the Indian to the UK. In only 5 patients with falciparum subcontinent (either holidaymakers or new immiinfection were both body weights and chloroquine grants) none of whom had received prophylaxis. dose recorded and all ofthese received a dose of less Four were Britons, 3 ofwhom were poor compliers. than 5 mg/kg base weekly.'2 Two were children Of the 44 cases, 93% were due to P. vivax, 28% receiving 2.2 and 2.3 mg/kg and 3 adults were using presenting within 1 month of return and 40% within 3 months, but 60% presented from 4 until 12 3.0, 3.6 and 4.3 mg/kg base weekly. months or longer after return. Morbidity, mortality and clinicalfindings Seasonal distribution in P. vivax patients There were no deaths. Fifteen cases had severe parasitaemia (> 10%) and 5 of these had renal Most patients presented between the months of failure, 2 cerebral malaria and 1 required a blood May and September. In our patients, month of transfusion. One patient had haemoptysis due to return and month of illness rose to a peak and fell thrombocytopenia and required platelet trans- during the year in concert for the whole group. fusions. Thrombocytopenia was very common, However, patients who had travelled to the Indian both in P. falciparum and P. vivax infections. subcontinent and returned to the UK during the Thirty-four patients (15%) had a concurrent winter months tended to develop malaria during the following summer. tropically acquired illness. Continent and country of origin
Discussion A total of 137 infections (60%) were acquired in Africa. Forty-four cases were from the Indian subcontinent, 19 from the Far East, 18 from New Guinea, 5 from the Middle East and 3 from South America. The country of origin was not recorded in 3 case notes. Patients returningfrom Africa
Of the 137 infections originating from Africa, two-thirds (66%) were due to P. falciparum (91 cases), 17% to P. vivax (24 cases), 3% each to P. ovale and P. malariae and in 10% (13 cases) no parasites were identified. Of these, 63% were Britons returning from travel or work in Africa and most of the remainder were African postgraduate students.
The populations of Lothian region and particularly of Edinburgh city have been gradually declining over the past 20 years and are currently 741,199 and 433,480, respectively, whilst the Borders region has stayed relatively static at 102,700.'3 Concomitantly, however, the number of foreign residents has been rising and in addition many temporary foreign residents include students and visitors to the Edinburgh Festival. The annual incidence of malaria, however, is only 1.7 per 10,000 for Borders and Lothian regions compared with 3.3 for the whole of the UK. This discrepancy is probably due in part to the magnetic role of LHTD which attracts a disproportionately large number of cases due to its location near the 3 London airports. Our study indicates that the average general practi-
24
L. WILLOCKS et al.
tioner in our area will see 1 case of malaria every were non-white British residents and their children 3-4 years with a 50% likelihood that this case will visiting abroad.'7 Clear guidelines for malarial prophylaxis have be due to potentially life-threatening P.falciparum. The increased incidence of infection which we been issued which recommend chloroquine, where found in men, young adults and children has been appropriate, to be used in a dose of 300 mg base previously documented3 and may be due to more weekly for adults and children over 12 years and adventurous travel in young adult males who may weighing 40 kg.'8 However, while the World comply less well with prophylaxis (as also may Health Organisation advises 300 mg weekly for children). adults weighing 50-70 kg'9 and 5 mg/kg for childThe proportion of falciparum cases increased ren under 40 kg,20 wide interindividual variation in from less than one third in 1969-73 to greater than blood concentrations are known to occur in adults half in 1984-88 in contrast to a survey in Leicester on the same dose, and there is only a weak where, from 1983-88 only one third had fal- correlation between whole blood concentration ciparum infections.'4 The Edinburgh results, how- and weight in those on regular long-term chloroever, concur with those for the UK as a whole in quine prophylaxis.2' Corachan and Gascon rewhich the incidence of P.falciparum malaria is now ported a retrospective study of 106 patients in 1988 greater than P. vivax.'5 presenting with malaria in Barcelona." Of these, 11 The absence of mortality in our cases compares had P. falciparum malaria and had taken prowith an overall UK average of 1 %15 and our phylaxis regularly before, during and after their complication and severe parasitaemia rate of 14% overseas trip. Nine of those who weighed more compares to about 75% in Leicester.'4 This than 75 kg had used 300 mg chloroquine weekly. indicates that where general practitioners refer Our own survey of this aspect was hampered by patients early to a Regional Infectious Diseases inadequate recording of body weight and dosage of Unit mortality is low even when the overall annual chloroquine prophylaxis but the limited data caseload of malaria for that Unit is relatively low. available support the contention that many adults A seasonal distribution of P. vivax malaria has using chloroquine may have taken an inadequate been demonstrated in 3 different UK centres.9"10"14 dose. In an era in which chloroquine resistance is a Walker's large study from Glasgow demonstrated major problem, clear data on the influence of body a marked discrepancy between month of return to weight on chloroquine pharmacokinetics are needthe UK and month of illness which, when com- ed in order to clarify a truly rational approach to pared to the seasonal distribution of travel to maximize the effectiveness of available chemoBombay and the rest of India, strongly suggested prophylactic regimes. that factors other than increased transmission during the summer months are involved.'0 Is a higher ambient temperature or humidity mediated Conclusions via humoral factors to the dormant hepatic hypnozoite needed to stimulate reactivation?9 Our own The incidence of malaria and of antimalarial drug results suggest that this may only be the case for resistance is increasing worldwide; with greater patients returning from the Indian subcontinent. ease of intercontinental travel, these problems are Subspecies differences in the behaviour of P. vivax reflected in a Scottish regional centre. The risks of parasites are known to occur.'6 A larger study is acquiring a potentially fatal plasmodium infection needed to confirm our observations that seasonal should be more widely publicized. Prophylaxis is reactivation of vivax malaria only occurs in still often taken irregularly or not at all and the patients from the Indian subcontinent. importance of this should be emphasized to travellers, in particular to travellers to popular Prophylaxis holiday areas such as Kenya and to Asians resident in the UK who are returning on holiday to their Prophylaxis is still taken irregularly or not at all, country of origin. Particular reference should be the most common failure being failure to continue paid to the importance of continuing prophylaxis prophylaxis on return to the UK. Failure to seek on return to the UK. However, many compliant any prophylaxis is particularly common among patients may have been receiving an inadequate Asians resident in the UK who are returning to the dose of chloroquine on a mg/kg basis. General Indian subcontinent on holiday. Many of these practitioners should not hesitate to contact the people believe themselves still to be immune. In a regional specialist unit whenever the diagnosis is study of malaria in the UK in 1982, one third (312) considered or whenever they have any doubts of UK patients presenting with P. vivax malaria concerning antimalarial prophylaxis.
CHANGING PATTERNS OF MALARIA
25
References 1. Tyler, D.J. Malaria - resurgence, resistance and research - 1. N Engl J Med 1983, 308: 875-878. 2. Tyler, D.J. Malaria - resurgence, resistance and research- 2. N Engl J Med 1983, 308: 934-940. 3. Phillips-Howard, P.A., Bradley, D.J., Blaze, M. & Hurn, M. Malaria in Britain: 1977-86. Br Med J 1988, 296: 245-248. 4. World Health Organisation. The epidemiology of drug resistant malaria parasites: memorandum from a WHO meeting. Bull WHO 1987, 65: 797-816. 5. Cook, G.C. Prevention and treatment of malaria. Lancet 1988, i: 32-37. 6. Rosaio, V.E., Hall, R., Walliker, D. & Beale, G.H. Persistence of drug resistant malaria parasites. Lancet 1978, i: 185-187. 7. Vachon, F., Le Tulzo, Y., Le Bras, J., Regnier, B. & Couland, J.P. Current severity of cerebral malaria. In: Kager, P.A. & Polderman, A.M. (eds). XIIth International Congress for Tropical Diseases and Malaria. Excerpta Medica, Amsterdam. International Congress Series 810, p. 86. 8. Simpson, R.McD. & Eden, O.B. Childhood malaria in Edinburgh 1961-82. Scot Med J 1988, 28: 350-354. 9. Warwick, R., Swimer, G.J. & Britt, R.P. Prolonged incubation period of imported P. vivax malaria in London. J R Soc Med 1980, 73: 333-336. 10. Walker, E. The seasonal pattern of Plasmodium vivax malaria in Glasgow. J Infect 1983, 7: 227-230. 11. Corachan, M. & Gascon, J. Malaria chemoprophylaxis and travellers' weight. Lancet 1988, ii: 791-792. 12. Onori, E. Malaria. In: Gilis, H.M. (ed.) Epidemiology and Control of Tropical Diseases. Clinics in Tropical Medicine and Communicable Diseases, Vol. 2, Saunders, London, 1986, pp. 491-496.
13. Population Statistics Branch, General Register Office for Scotland. (Personal communication.) 14. Wiselka, M.J., Kent, J. & Nicholson, K.G. Malaria in Leicester 1983-88: a review of 114 cases. J Infect 1983, 7: 227-230. 15. Bradley, D.J. Current trends in malaria in Britain. J R Soc Med 1989, 82 (Suppl): 8-14. 16. Jiang, J.B., Huang, J.C., Liang, D.S. et al. Long incubation period Plasmodium vivax multinucleatum as demonstrated in three experimental human cases. Trans R Soc Trop Med Hyg 1982, 76: 845-846. 17. Public Health Laboratory Service Malaria Reference Laboratory and the Communicable Disease Surveillance Centre. Malaria in Britain: 1982. Br Med J 1983, 287: 1789. 18. Bradley, D.J. & Phillips-Howard, P.A. Prophylaxis against malaria for travellers from the United Kingdom. Br Med J 1989, 299: 1087- 1089. 19. World Health Organisation. Vaccination Certificate Requirements and Health Advice for International Travel. WHO, Geneva, 1988, p. 47. 20. Lobel, H.O. & Campbell, G.C. Malaria prophylaxis and distribution of drug resistance. In: Strickland, G.T. (ed.) Malaria. W.B. Saunders, London, 1986, p. 235. 21. Rombo, L., Bergquist, Y. & Hellgren, U. Chloroquine and desethyl chloroquine concentrations during regular long term malaria prophylaxis. Bull WHO 1987, 65: 879-883.
D The Fellowship of Postgraduate Medicine,
1992
Changing patterns of malaria in south-east Scotland: implications for practitioner awareness and prophylactic advice Lorna Willocks, Michael Jones, Ray Brettle, Philip Welsby and James Gray Infectious Diseases Unit, City Hospital, Greenbank Drive, Edinburgh, EHIO 5SB, UK
Summary: The medical records of all 229 patients with malaria admitted to the Edinburgh City Hospital between 1969 and 1988 were studied retrospectively. A total of 137 were from Africa, 44 from the Indian subcontinent, 19 from the Far East, 18 from New Guinea, 5 from the Middle East and 3 from South America. The number of yearly admissions rose markedly after 1983, mainly due to an increase in Plasmodiumfalciparum cases. Ninety-four cases (15 with severe parasitaemia) mainly from Kenya and Nigeria were due to P. fakciparum infection and 99 to P. vivax. There were no deaths. A seasonal distribution of onset of fever in patients with P. vivax infections originating from the Indian subcontinent showed that most patients presented during the summer. Prophylaxis had generally been irregular or non-existent but many compliant patients may have been receiving an inadequate dose of chloroquine on a mg/kg body weight basis. General practitioners are Ukely to see at least one case of malaria every 4 years. They are encouraged to seek advice from a specialist unit whenever necessary whether before or after their patient travels abroad. Travellers, in particular to Kenya and Nigeria, and Asian immigrants to the UK returning on holiday to their country of origin should be strongly advised to take regular prophylaxis including on return to the UK. Introduction
The last 20 years have witnessed a dramatic change in the incidence, species proportions, drug resistance and geographical distribution of malaria worldwide.',2 In 1970 only 49 cases of Plasmodium falciparum infection were notified in the UK rising to 1,028 in 1988 with the percentage of UK cases seen at the Hospital for Tropical Diseases, London (LHTD) falling from 65% in 1970 to 30% in 1988 (Chiodini, personal communication). Therefore while the number of cases at LHTD has risen ten-fold, the number of cases of P. falciparum seen elsewhere in the UK has risen twenty-fold. Over the ten years 1977-86 the annual incidence of malaria in the UK increased by 51% from 1,529 to 2,309 cases and the proportion of cases due to P. falciparum increased from one fifth to one third.3 Chloroquine resistance in P. falciparum malaria has become widespread4'5 and it may be increasing in virulence.6'7 The only previous study of malaria in Edinburgh was confined to children.8 We conducted a retrospective survey of malaria presenting in Edinburgh
City Hospital from 1969 to 1988 to determine the extent to which national trends are being reflected in a Scottish Regional Centre. We also examined the monthly incidence of P. vivax malaria to determine whether a seasonal pattern of P. vivax malaria reported elsewhere in the UK9"0 is observed in Edinburgh and the possibility that breakthrough malaria in some patients may be associated with inadequate doses of chloroquine prophylaxis on a mg/kg body weight basis." Methods
Admissions in Edinburgh with malaria for the years 1969-1988 inclusive were identified from Scottish hospital inpatient statistics and City Hospital case notes. The City Hospital Tropical Medicine Unit (1961-1972) and Infectious Diseases Unit (1972 onwards) was the site of referral for patients with malaria from south-east Scotland throughout the period under study. Results
Correspondence: L. Willocks, M.R.C.P. Accepted: 2 September 1991
Of 229 admissions the male to female ratio of 164:65 (i.e. 3: 1) remained constant throughout.
CHANGING PATTERNS OF MALARIA
23
The mean age was 29 years (range 2-80). The Four countries (Nigeria, Kenya, Ghana and number of cases per year rose over the period Tanzania) accounted for 65% of cases. One third studied from a mean of 10.6 patients per year in the (6/15) ofall cases presenting to our Unit with severe first 5 years (53 admissions) to 15.2 patients per parasitaemia or complicated malaria originated year in the last 5 years (76 admissions). The most from Kenya and Nigeria. Most complications marked increase has been since 1983 and was related to thrombocytopenia with subsequent bleeding. Two patients (one of whom required largely due to P. falciparum malaria. exchange transfusion for 30% parasitaemia) from Nigeria had cerebral malaria and renal failure Species requiring dialysis and I from Kenya was dialysed There were 99 cases due to Plasmodium vivax, 94 to for blackwater fever. P. falciparum, 6 to P. ovale, 5 to P. malariae and 3 to mixed infections. Parasite speciation was not Patients returningfrom the Indian subcontinent performed in 22 patients. From 1985 onwards parasites were identified in all cases and comprised Forty-four patients presented from the Indian subcontinent, the annual incidence increasing only falciparum or vivax species. markedly over the first 15 years and falling over the last 5. Most (31) patients were settled immigrants Prophylaxis returning from holidays in their country of origin. Most prophylaxis was inadequate, the most com- Twenty-two had taken no prophylaxis and 8 were mon failure being irregular prophylaxis after return poor compliers. Nine were visitors from the Indian to the UK. In only 5 patients with falciparum subcontinent (either holidaymakers or new immiinfection were both body weights and chloroquine grants) none of whom had received prophylaxis. dose recorded and all ofthese received a dose of less Four were Britons, 3 ofwhom were poor compliers. than 5 mg/kg base weekly.'2 Two were children Of the 44 cases, 93% were due to P. vivax, 28% receiving 2.2 and 2.3 mg/kg and 3 adults were using presenting within 1 month of return and 40% within 3 months, but 60% presented from 4 until 12 3.0, 3.6 and 4.3 mg/kg base weekly. months or longer after return. Morbidity, mortality and clinicalfindings Seasonal distribution in P. vivax patients There were no deaths. Fifteen cases had severe parasitaemia (> 10%) and 5 of these had renal Most patients presented between the months of failure, 2 cerebral malaria and 1 required a blood May and September. In our patients, month of transfusion. One patient had haemoptysis due to return and month of illness rose to a peak and fell thrombocytopenia and required platelet trans- during the year in concert for the whole group. fusions. Thrombocytopenia was very common, However, patients who had travelled to the Indian both in P. falciparum and P. vivax infections. subcontinent and returned to the UK during the Thirty-four patients (15%) had a concurrent winter months tended to develop malaria during the following summer. tropically acquired illness. Continent and country of origin
Discussion A total of 137 infections (60%) were acquired in Africa. Forty-four cases were from the Indian subcontinent, 19 from the Far East, 18 from New Guinea, 5 from the Middle East and 3 from South America. The country of origin was not recorded in 3 case notes. Patients returningfrom Africa
Of the 137 infections originating from Africa, two-thirds (66%) were due to P. falciparum (91 cases), 17% to P. vivax (24 cases), 3% each to P. ovale and P. malariae and in 10% (13 cases) no parasites were identified. Of these, 63% were Britons returning from travel or work in Africa and most of the remainder were African postgraduate students.
The populations of Lothian region and particularly of Edinburgh city have been gradually declining over the past 20 years and are currently 741,199 and 433,480, respectively, whilst the Borders region has stayed relatively static at 102,700.'3 Concomitantly, however, the number of foreign residents has been rising and in addition many temporary foreign residents include students and visitors to the Edinburgh Festival. The annual incidence of malaria, however, is only 1.7 per 10,000 for Borders and Lothian regions compared with 3.3 for the whole of the UK. This discrepancy is probably due in part to the magnetic role of LHTD which attracts a disproportionately large number of cases due to its location near the 3 London airports. Our study indicates that the average general practi-
24
L. WILLOCKS et al.
tioner in our area will see 1 case of malaria every were non-white British residents and their children 3-4 years with a 50% likelihood that this case will visiting abroad.'7 Clear guidelines for malarial prophylaxis have be due to potentially life-threatening P.falciparum. The increased incidence of infection which we been issued which recommend chloroquine, where found in men, young adults and children has been appropriate, to be used in a dose of 300 mg base previously documented3 and may be due to more weekly for adults and children over 12 years and adventurous travel in young adult males who may weighing 40 kg.'8 However, while the World comply less well with prophylaxis (as also may Health Organisation advises 300 mg weekly for children). adults weighing 50-70 kg'9 and 5 mg/kg for childThe proportion of falciparum cases increased ren under 40 kg,20 wide interindividual variation in from less than one third in 1969-73 to greater than blood concentrations are known to occur in adults half in 1984-88 in contrast to a survey in Leicester on the same dose, and there is only a weak where, from 1983-88 only one third had fal- correlation between whole blood concentration ciparum infections.'4 The Edinburgh results, how- and weight in those on regular long-term chloroever, concur with those for the UK as a whole in quine prophylaxis.2' Corachan and Gascon rewhich the incidence of P.falciparum malaria is now ported a retrospective study of 106 patients in 1988 greater than P. vivax.'5 presenting with malaria in Barcelona." Of these, 11 The absence of mortality in our cases compares had P. falciparum malaria and had taken prowith an overall UK average of 1 %15 and our phylaxis regularly before, during and after their complication and severe parasitaemia rate of 14% overseas trip. Nine of those who weighed more compares to about 75% in Leicester.'4 This than 75 kg had used 300 mg chloroquine weekly. indicates that where general practitioners refer Our own survey of this aspect was hampered by patients early to a Regional Infectious Diseases inadequate recording of body weight and dosage of Unit mortality is low even when the overall annual chloroquine prophylaxis but the limited data caseload of malaria for that Unit is relatively low. available support the contention that many adults A seasonal distribution of P. vivax malaria has using chloroquine may have taken an inadequate been demonstrated in 3 different UK centres.9"10"14 dose. In an era in which chloroquine resistance is a Walker's large study from Glasgow demonstrated major problem, clear data on the influence of body a marked discrepancy between month of return to weight on chloroquine pharmacokinetics are needthe UK and month of illness which, when com- ed in order to clarify a truly rational approach to pared to the seasonal distribution of travel to maximize the effectiveness of available chemoBombay and the rest of India, strongly suggested prophylactic regimes. that factors other than increased transmission during the summer months are involved.'0 Is a higher ambient temperature or humidity mediated Conclusions via humoral factors to the dormant hepatic hypnozoite needed to stimulate reactivation?9 Our own The incidence of malaria and of antimalarial drug results suggest that this may only be the case for resistance is increasing worldwide; with greater patients returning from the Indian subcontinent. ease of intercontinental travel, these problems are Subspecies differences in the behaviour of P. vivax reflected in a Scottish regional centre. The risks of parasites are known to occur.'6 A larger study is acquiring a potentially fatal plasmodium infection needed to confirm our observations that seasonal should be more widely publicized. Prophylaxis is reactivation of vivax malaria only occurs in still often taken irregularly or not at all and the patients from the Indian subcontinent. importance of this should be emphasized to travellers, in particular to travellers to popular Prophylaxis holiday areas such as Kenya and to Asians resident in the UK who are returning on holiday to their Prophylaxis is still taken irregularly or not at all, country of origin. Particular reference should be the most common failure being failure to continue paid to the importance of continuing prophylaxis prophylaxis on return to the UK. Failure to seek on return to the UK. However, many compliant any prophylaxis is particularly common among patients may have been receiving an inadequate Asians resident in the UK who are returning to the dose of chloroquine on a mg/kg basis. General Indian subcontinent on holiday. Many of these practitioners should not hesitate to contact the people believe themselves still to be immune. In a regional specialist unit whenever the diagnosis is study of malaria in the UK in 1982, one third (312) considered or whenever they have any doubts of UK patients presenting with P. vivax malaria concerning antimalarial prophylaxis.
CHANGING PATTERNS OF MALARIA
25
References 1. Tyler, D.J. Malaria - resurgence, resistance and research - 1. N Engl J Med 1983, 308: 875-878. 2. Tyler, D.J. Malaria - resurgence, resistance and research- 2. N Engl J Med 1983, 308: 934-940. 3. Phillips-Howard, P.A., Bradley, D.J., Blaze, M. & Hurn, M. Malaria in Britain: 1977-86. Br Med J 1988, 296: 245-248. 4. World Health Organisation. The epidemiology of drug resistant malaria parasites: memorandum from a WHO meeting. Bull WHO 1987, 65: 797-816. 5. Cook, G.C. Prevention and treatment of malaria. Lancet 1988, i: 32-37. 6. Rosaio, V.E., Hall, R., Walliker, D. & Beale, G.H. Persistence of drug resistant malaria parasites. Lancet 1978, i: 185-187. 7. Vachon, F., Le Tulzo, Y., Le Bras, J., Regnier, B. & Couland, J.P. Current severity of cerebral malaria. In: Kager, P.A. & Polderman, A.M. (eds). XIIth International Congress for Tropical Diseases and Malaria. Excerpta Medica, Amsterdam. International Congress Series 810, p. 86. 8. Simpson, R.McD. & Eden, O.B. Childhood malaria in Edinburgh 1961-82. Scot Med J 1988, 28: 350-354. 9. Warwick, R., Swimer, G.J. & Britt, R.P. Prolonged incubation period of imported P. vivax malaria in London. J R Soc Med 1980, 73: 333-336. 10. Walker, E. The seasonal pattern of Plasmodium vivax malaria in Glasgow. J Infect 1983, 7: 227-230. 11. Corachan, M. & Gascon, J. Malaria chemoprophylaxis and travellers' weight. Lancet 1988, ii: 791-792. 12. Onori, E. Malaria. In: Gilis, H.M. (ed.) Epidemiology and Control of Tropical Diseases. Clinics in Tropical Medicine and Communicable Diseases, Vol. 2, Saunders, London, 1986, pp. 491-496.
13. Population Statistics Branch, General Register Office for Scotland. (Personal communication.) 14. Wiselka, M.J., Kent, J. & Nicholson, K.G. Malaria in Leicester 1983-88: a review of 114 cases. J Infect 1983, 7: 227-230. 15. Bradley, D.J. Current trends in malaria in Britain. J R Soc Med 1989, 82 (Suppl): 8-14. 16. Jiang, J.B., Huang, J.C., Liang, D.S. et al. Long incubation period Plasmodium vivax multinucleatum as demonstrated in three experimental human cases. Trans R Soc Trop Med Hyg 1982, 76: 845-846. 17. Public Health Laboratory Service Malaria Reference Laboratory and the Communicable Disease Surveillance Centre. Malaria in Britain: 1982. Br Med J 1983, 287: 1789. 18. Bradley, D.J. & Phillips-Howard, P.A. Prophylaxis against malaria for travellers from the United Kingdom. Br Med J 1989, 299: 1087- 1089. 19. World Health Organisation. Vaccination Certificate Requirements and Health Advice for International Travel. WHO, Geneva, 1988, p. 47. 20. Lobel, H.O. & Campbell, G.C. Malaria prophylaxis and distribution of drug resistance. In: Strickland, G.T. (ed.) Malaria. W.B. Saunders, London, 1986, p. 235. 21. Rombo, L., Bergquist, Y. & Hellgren, U. Chloroquine and desethyl chloroquine concentrations during regular long term malaria prophylaxis. Bull WHO 1987, 65: 879-883.
